Regularized weighted sine least-squares spectral analysis for gas electron diffraction data

Here, we present a new approach for obtaining radial distribution functions (RDF) from the electron diffraction data using a regularized weighted sine least-squares spectral analysis. It allows for explicitly transferring the measured experimental uncertainties in the reduced molecular scattering function to the produced RDF. We provide a numerical demonstration, discuss the uncertainties and correlations in the RDFs, and suggest a regularization parameter choice criterion. The approach is also applicable for other diffraction data, e.g., for x-ray or neutron diffraction of liquid samples.

Structural Changes Induced by Quinones: High-Resolution Microwave Study of 1,4-Naphthoquinone

1,4-Naphthoquinone (1,4-NQ) is an important product of naphthalene oxidation, and it appears as a motif in many biologically active compounds. We have investigated the structure of 1,4-NQ using chirped-pulse Fourier transform microwave spectroscopy and quantum chemistry calculations. The rotational spectra of the parent species, and its 13 C and 18 O isotopologues were observed in natural abundance, and their spectroscopic parameters were obtained. This allowed the determination of the substitution rs , mass-weighted rm and semi-experimental reSE structures of 1,4-NQ. The obtained structural parameters show that the quinone moiety mainly changes the structure of the benzene ring where it is inserted, modifying the C-C bonds to having predominantly single or double bond character. Furthermore, the molecular electrostatic surface potential reveals that the quinone ring becomes electron deficient while the benzene ring remains a nucleophile. The most electrophilic areas are the hydrogens attached to the double bond in the quinone ring. Knowledge of the nucleophilic and electrophilic areas in 1,4-NQ will help understanding its behaviour interacting with other molecules and guide modifications to tune its properties.